Gas-treatment devices

ABSTRACT

An HME for a tracheostomy tube has a flexible outer housing of a gas-permeable material containing an HME element of discrete particles, granules or the like of a hygroscopic material. The particles are contained between the outer housing and an inner wall of a foam. The inner wall has a ciliated surface facing the end of the tube, which acts to distribute gas over the surface of the HME element. The HME is attached to a flange on an inner cannula by means of a removable adhesive. The HME may include a suction port through a self-closing aperture, which makes a wiping seal with a suction catheter inserted in the tube.

BACKGROUND OF THE INVENTION

This invention relates to gas-treatment devices.

The invention is more particularly concerned with heat and moistureexchangers (HMEs) or the like for use with tracheostomy tubes.

In normal breathing, inhaled air passes through the nose where it iswarmed and moistened before passing to the trachea and bronchialpassages. Where a patient breathes via a tracheal tube or laryngealmask, gas is supplied directly to the trachea, by-passing the nose. Thegas is, therefore, preferably warmed and moistened to prevent discomfortand damage to the lining of the trachea. This is often achieved by aheat and moisture exchange device or HME connected to the tracheal tubeto receive both exhaled and inhaled gases. The HME has amoisture-absorbing element, such as of a treated paper or foam, thatabsorbs moisture in exhaled gases and transfers a major part of this tothe inhaled gases. The element also warms inhaled gas in the same way.HMEs are sold by Portex Limited of Hythe, England under the trade markThermovent. Examples of HMEs are described in: GB 2303307; GB 2321600;GB 2277689; GB 2268496; GB2267840; GB 2233904; EP 535016; EP 533644; EP387220; EP 265163; EP 413127; U.S. Pat. No. 4,516,573; U.S. Pat. No.4,090,513; U.S. Pat. No. 4,771,770; U.S. Pat. No. 4,200,094; and U.S.Pat. No. 4,048,993. The HME may also include a filter for removingparticles, bacteria and viruses from gas supplied to or from thepatient.

Conventional HMEs have an exchange element within a rigid housing thatis coupled to the machine end of the tracheal tube. This can berelatively bulky and is a particular problem where the patient isbreathing unaided via a tracheostomy tube since it is preferable forthis to be as unobtrusive as possible.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an alternativegas-treatment device and assembly.

According to one aspect of the present invention there is provided agas-treatment device for connection to the machine end of a patientbreathing tube, the device being conformable.

The device preferably includes a flexible outer housing and agas-treatment element that is substantially conformable to the shape ofthe outer housing. The outer housing is preferably of a gas-permeablematerial, such as a fabric. The device preferably includes an HMEelement. The HME element may include a discrete material, such as in theform of particles, granules or small balls. The HME element may includea zeolite. The device may include a flexible outer housing, aconformable gas-treatment element within the housing and gas-dispersionmeans within the housing arranged to disperse gas over the gas-treatmentelement. The gas-dispersion means may include a ciliated surface. Thepatient breathing tube is preferably a tracheostomy tube. Thegas-treatment device may be supported on a flange of the tube and ispreferably removably attached with the flange, such as by means of anadhesive. The breathing tube preferably has a coupling extending withinthe gas-treatment device, the coupling having at least one side port.The gas-treatment device may include a self-sealing port arranged to bealigned with the machine end of the breathing tube such as to enable anelongate member to be inserted through the port and the device, into thetube. The port is preferably arranged to make a wiping seal with theelongate member.

According to another aspect of the present invention there is provided agas-treatment device including a port for connection to a patientbreathing tube and a gas-treatment element, the device including anouter wall of gas-permeable material such that gas passes to and fromthe patient breathing tube via the port, the gas-treatment element andthrough the outer wall.

The wall may be of a fabric and the gas-treatment element may be an HMEelement. The HME element may include a discrete material, such as in theform of particles, granules or small balls.

According to a further aspect of the present invention there is providedan assembly of a breathing tube and a gas-treatment device according tothe above one or other aspect of the invention.

The breathing tube preferably includes an outer tube and a removableinner cannula inserted within the outer tube, the gas-treatment devicebeing mounted at the machine end of the inner cannula.

A tracheostomy tube assembly including an HME, in accordance with thepresent invention, will now be described, by way of example, withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of the assembly;

FIG. 2 is a partly cross-sectional view of a part of the assemblyshowing the HME; and

FIG. 3 is a partly cross-sectional view of a part of an alternativeassembly having a modified HME.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference first to FIGS. 1 and 2, the assembly comprises an outer,tracheostomy tube 1, a removable inner cannula or liner 2 and an HMEgas-treatment device 3 connected to the machine end of the cannula. Wheninserted, the inner cannula 2 is considered to form a part of thetracheostomy tube 1.

The tracheostomy tube 1 is conventional having a shaft 10 curved to theanatomy of the patient so that, in use, its patient end 11 is directedcaudally within the trachea. The machine end 12 of the tube 1 terminatesflush with a laterally-extending flange 13 shaped to lie flat on thepatient's skin to either side of the tracheostomy.

The cannula 2 has a shaft 20 curved to the same shape as thetracheostomy tube 1 and its external diameter is such that it is a closesliding fit within the tracheostomy tube. The cannula 2 also has aflange 23 at its machine end 22 of the same shape as the flange 13 ofthe tracheostomy tube so that the two flanges lie close to one anotherwhen assembled. A short cylindrical coupling 24 projects from the rear,machine side of the flange 23. The coupling 24 has a tapered female boreadapted to receive a 15 mm male coupling and it also has a number ofside ports 25 equally spaced around its circumference. The side ports 25are arranged so that they will be occluded when a male coupling or 15 mmconnector is inserted.

The HME 3 is fitted over the coupling 24 and is attached to the flange23. The HME 3 has an outer wall or housing 30 of a bonded-fibre fabricor other gas-permeable flexible material, such as a perforated material.The housing 30 has a generally rectangular shape, when viewed along theaxis of the cannula 2, that follows approximately the outline of theflange 23. Alternatively, the housing could be oval or elliptical viewedalong the axis of the cannula. In section, as shown in FIG. 2, thehousing 30 is oval. Centrally in one side of the housing 30 there is acircular aperture 31 the diameter of which is approximately equal to theexternal diameter of the coupling 24. A region 32 on the outside of thehousing 30 around the aperture 31 has a low-tack adhesive, which forms asecure, gas-tight seal with the machine side of the flange 23. The HMEcould be attached to the cannula in other ways, such as by a mechanicalclasp or by hook-and-loop fabric. The coupling 24 projects through theaperture 31 into a central cavity 33 within the housing 30. The cavity33 is enclosed by a porous foam sponge wall or insert 35 having multiplefingers 36 projecting inwardly towards the aperture 31 to provide aciliated surface 37 to the cavity.

The HME 3 is completed by an HME element 38 located between the wall 30and the foam insert 35. The element 38 extends along the machine-endface 39 of the housing 30 and the edges 40 but not along the major partof the patient-end face 41 in the region 32 because contact with theflange 23 in this region prevents passage of gas. The HME element 38 isof a discrete material, that is, it is formed of separate discretepieces so that it can conform freely to the shape of the housing 30. Inparticular, the element 38 is formed from particles 42 of zeolites,which act as molecular sieves, or small balls of foam or paper treatedwith a hygroscopic material of the kind commonly used in HME paperelements.

The HME 3, therefore, has a soft, conformable nature of the same kind asa bean bag and can be laid substantially flat over the machine side ofthe flange 23.

In use, the cannula 2 is inserted in the tracheostomy tube 1 of apatient who is breathing spontaneously. The two flanges 13 and 23 aresecured together to hold the cannula 2 in position. When the patientexhales, air flows along the bore of the inner cannula 2, through thecoupling 24, via its open end and the side ports 25, into the cavity 33within the HME 3. The fingers 36 of the sponge element 35 distribute theair over the entire surface of the HME element 38 for maximum efficiencyso that the major part of the heat and moisture in the exhaled breath istransferred to the element. The foam member 35 also takes some part inabsorbing the heat and moisture. The gas then flows out through the wall30 of the HME 3 over a relatively large area. When the patient inhales,air flows in through the wall 30, through the element 38 and the foam 35taking up the major part of the heat and moisture absorbed in theseparts. The warmed and moistened air then flows through the coupling 24along the tracheostomy tube 1, via the inner cannula 2, to the patient.

The arrangement of the present invention enables a low profile HME to beprovided, which is inconspicuous, does not interfere with bedding andclothing and produces less leverage on the tube to which it isconnected. The HME presents a conformable external surface, which alsomakes it comfortable where it comes into contact with the skin. Theporous nature of the wall acts as a coarse filter preventing inhalationof larger particles and insects etc. Because the air flows in and outover a large area there is a reduced risk of occlusion.

The inner cannula with the HME is removed and replaced periodically whensecretions start to collect. It will be appreciated, however, that theHME could be attached directly to the flange of the tracheostomy tubewhere an inner cannula is not used, the HME being removed and replacedas necessary. If access is needed to the coupling 24, such as to connectthe patient to a ventilator or resuscitator, the HME can be readilyremoved by pulling apart the adhesive join at the region 32.

The HME could be modified to allow use of a suction catheter, endoscopeor other elongate member, as shown in FIG. 3 where similar componentshave been given the same reference number with the addition of 100. Thehousing 130 is of a similar shape to the housing 30 shown in FIG. 2 butit has a second aperture 151 located directly opposite the aperture 131in which the coupling 124 is received. The second aperture 151 differsfrom the first in that it is normally closed, being formed by a passagethrough the foam member 135, which is extended to the wall 130 aroundthe aperture. The aperture 151 is closed resiliently by the nature ofthe foam but can be opened when it is necessary to insert a suctioncatheter 200 or the like along the tracheostomy tube simply by pushingthe catheter through the aperture. The foam member 135 around theaperture 151 contacts the catheter 200 around its circumference toprovide a wiping seal that restricts the escape of gas through theaperture around the outside of the catheter.

The invention, in some of its aspects, is not confined to HMEs but couldbe used with other gas-treatment devices such as filters.

1. A gas-treatment device comprising a housing, a gas-treatment elementand an inlet for connection to a machine end of a patient breathingtube, wherein said device is conformable:
 2. A gas-treatment deviceaccording to claim 1, wherein said housing is flexible and wherein saidhousing contains a gas-treatment element that substantially conforms tothe shape of the housing.
 3. A gas-treatment device according to claim2, wherein said housing is of a gas-permeable material.
 4. Agas-treatment device according to claim 3, wherein said housing is of afabric.
 5. A gas-treatment device according to claim 1, wherein saidgas-treatment element is an HME element.
 6. A gas-treatment deviceaccording to claim 5, wherein said HME element includes a discretematerial.
 7. A gas-treatment device according to claim 6, wherein saiddiscrete material is in the form of particles, granules or small balls.8. A gas-treatment device according to claim 5, wherein said HME elementincludes a zeolite.
 9. A gas-treatment device according to claim 1,wherein said housing is flexible, wherein said gas-treatment element isconformable, and wherein said housing contains a gas-disperser arrangedto disperse gas over said gas-treatment element.
 10. A gas-treatmentdevice according to claim 9, wherein said gas-disperser includes aciliated surface.
 11. A gas-treatment device according to claim 1,wherein said patient breathing tube is a tracheostomy tube.
 12. Agas-treatment device according to claim 1, wherein said tube has aflange at its machine end, and wherein said gas-treatment device issupported on said flange.
 13. A gas-treatment device according to claim12, wherein said gas-treatment device is removably attached with saidflange.
 14. A gas-treatment device according to claim 12, wherein saidgas-treatment device is attached with said flange by means of anadhesive.
 15. A gas-treatment device according to claim 1, wherein saidbreathing tube has a coupling extending within said gas-treatmentdevice, and wherein said coupling has at least one side port.
 16. Agas-treatment device according to claim 1, including a self-sealing portarranged to be aligned with a machine end of said breathing tube such asto enable an elongate member to be inserted through said port and saiddevice, into said tube.
 17. A gas-treatment device according to claim16, wherein said port is arranged to make a wiping seal with saidelongate member.
 18. A gas-treatment device comprising an outer wall ofa gas-permeable material, a gas-treatment element within said outerwall, and a port for connection to a patient breathing tube such thatgas passes to and from said patient breathing tube via said port, saidgas-treatment element and through said outer wall.
 19. A gas-treatmentdevice according to claim 18, wherein said wall is of a fabric.
 20. Agas-treatment device according to claim 18, wherein said gas-treatmentelement is an HME element.
 21. A gas-treatment device according to claim20, wherein said HME element includes a discrete material.
 22. Agas-treatment device according to claim 21, wherein said discretematerial is in the form of particles, granules or small balls.
 23. Anassembly comprising: a breathing tube having a patient end and a machineend, and a gas-treatment device connected at said machine end of saidbreathing tube, wherein said gas-treatment device is conformable.
 24. Anassembly according to claim 23, wherein said breathing tube includes anouter tube and a removable inner cannula inserted within said outertube, and wherein said gas-treatment device is mounted at a machine endof said inner cannula.
 25. An HME comprising: an outer flexible wall ofgas-permeable material; an inner porous wall within the outer flexiblewall; an HME element of a discrete material between said outer and innerwalls that conforms to the shape of said walls; a inner cavity dividedfrom said HME element by said porous wall; and an opening into saidcavity by which gas can be supplied to and from said cavity and throughsaid inner wall, said HME element and said outer wall.
 26. An assemblycomprising: a breathing tube having a patient end and a machine end; agas-treatment device comprising an outer wall of a gas-permeablematerial, a gas-treatment element within said outer wall, and a portconnected to a patient breathing tube such that gas passes to and fromsaid patient breathing tube via said port, said gas-treatment elementand through said outer wall.
 27. An assembly according to claim 26,wherein said gas-treatment device is an HME.
 28. An assembly comprising:a breathing tube having a patient end and a machine end; a flange atsaid machine end; and a gas-treatment device mounted on said flange andpresenting a conformable external surface.
 29. An assembly according toclaim 28, wherein said gas-treatment device is an HME.